DE4036265A1 - Strip material for shaping - has unidirectional reinforcement and matrix fibres to give local bonding on at least one surface - Google Patents

Abstract

Strip material to be used for shaping in a press is composed of unidirectional reinforcement and thermoplastic matrix fibres and uses yarns contg. the reinforcement and/or matrix fibres. The yarn density is about 5-20 yarns/cm across the material width, using 1000-3000 dtex yarns. The matrix fibres are secured at local bonding points, at least at one surface of the material, by melting on or into the fabric. Pref. the material is composed of a mixt. of yarns of reinforcement and matrix fibres, or a mixed yarn of the two fibres types, or of bicomponent fibres with a reinforcement and a matrix component. The bonding points are formed in a regular repeating pattern, or they are in a static distribution over the material surface, to form 5-50% of the material surface.

Description

The present invention relates to strip-shaped semi-finished products, which are used to manufacture composite materials, Particularly suitable for fiber-reinforced thermoplastics.

It is already known to manufacture fiber reinforced Thermoplastics use so-called "organic sheets". These generally consist of tapes Reinforcing fibers made with thermoplastic material are melt impregnated. Such semi-finished products are stiff and do not have the drapability of textile fabrics.

From DE-C-23 20 133 nonwovens are unidirectional arranged carbon fibers known with adhesive are impregnated and which are perpendicular to the Carbon fiber threads made of thermoplastic Material held together by melting these threads will. DE-GBM 85 21 108 describes textile reinforcements for the production of layered structures from longitudinal and Cross thread layers. The number of crossing points kept as low as possible between warp and weft threads. This is made more superimposed there by an arrangement Longitudinal and transverse thread layers achieved by additional Longitudinal threads of thermoplastic material with each other are connected. Further configurations of Textile reinforcements are in EP-B-1 93 478, EP-B-1 93 479 and EP-B-1 98 776. From EP-A-1 44 939 a composite material made of warp and weft threads Reinforcing fibers are known, wherein the warp and / or Weft threads with threads made of thermoplastic material are wrapped, the welding by heating the Reinforcing fibers causes.  

All these embodiments have in common that they are threads have different orientations.

Furthermore, DE-A-18 08 286 nonwovens are disclosed which consist of statistically stored threads or fibers and the at least one thermoplastic polymer material exhibit. These nonwovens are characterized by that in some of the nonwoven fabric there is a consolidation was made, in this part a certain Number of tie points per unit area with one certain cross-sectional area of the bond point peaks has been. The consolidation is e.g. B. by treatment of Fleece with a heated press that is structured Surface has achieved.

Finally, DE-A-34 08 769 describes a method for Manufacture of fiber-reinforced molded articles thermoplastic material known in the flexible textile Formations are used that are largely unidirectional or reinforcement fibers aligned in parallel and out one made of thermoplastic yarns or fibers Matrix exist. It is essentially knitted these fibers described or strands or ribbons. These Semi-finished products are then only in their final shaping deformed by heatable profile nozzles, practically all thermoplastic fibers are melted.

New textile semi-finished products have now been found, one have good drapability and especially in let structured molds be processed. The Semi-finished products according to the invention essentially have one homogeneous distribution between the different types of fibers on and the orientation of the reinforcing fibers is largely unidirectional. The drapability of the semi-finished product according to the invention corresponds approximately to that of one Woven or knitted fabric of the same basis weight from these Fibers and has a fabric or knitted fabric Advantage that the fibers are unidirectionally aligned and thus an alignment of the fibers by stretching during downstream thermal shaping process are eliminated can.  

The invention relates essentially to a tape unidirectional reinforcement fibers and thermoplastic matrix fibers. Characteristic of the tape according to the invention is that this essentially consists of Yarns, the reinforcing fibers and / or matrix fibers included, the yarn density of the tape is about 5 is up to 20 yarns / cm width, the titer of the yarns is about 1000 to 3000 dtex and the matrix fibers at least on one surface of the strip to form Solidification points are locally melted or melted.

The term "yarn" is used for the purposes of this application Multifilament yarns, staple fiber yarns, mixed yarns Multifilaments and staple fibers and also monofilaments too understand. The term "fiber" means in the sense of this Registration of both staple fibers and endless filaments too understand.

The yarn density of the tape is chosen so that the distance the yarn making up the tape does not become too large, so that the formation of solidification points between neighboring ones Yarn is still possible. Usually the distance should be the yarns in the ribbon are less than about three times Diameter of a monofilament from the titer of the yarn. The titer the yarns used from reinforcement and / or Matrix fibers are usually 1000 to 3000 dtex, preferably 1500 to 2500 dtex.

Reinforcing fibers and matrix fibers can both be in shape separate yarns are available as well as mixed yarns. Further can also bicomponent fibers made of reinforcement and Matrix components are used. Lying in the yarn the reinforcing fibers preferably in the form of Multifilaments. It is particularly preferably used Blended yarns made from reinforcement and matrix fibers.  

Blended yarns can be used in any of the usual ways Mixing techniques are produced, such as. B. ring or 3-cylinder spinning, commingeling techniques, mixed twine manufacturing or DREF techniques.

Multifilament blended yarns are particularly preferably used of reinforcing and matrix fibers, in which at least one Part of the yarn made from high modulus single filaments Initial module of more than 50 GPa, especially more than 80 GPa, which is obtained by mixing using a Mixing medium, preferably air, are available, the high modulus single filaments before mixing a temperature of 0.25 Ts to 0.9 Ts has been preheated and the mixing takes place at a temperature in which the matrix fibers are essentially preserved; in particular, the mixing in the unheated Mixing medium carried out. Ts means the Melting or decomposition temperature of the High modulus single filaments in ° C.

These are particularly preferred multifilament blended yarns characterized in that the average Intermixing distance of the yarn, measured in the needle test, is less than 150 mm and that the number of breaks of the Individual filaments, measured using the light barrier method one side of the yarn is less than 20 / m.

Virtually none of them come as reinforcing fibers fusible or high-fusible, high-modulus and / or high-strength fibers in question. These fibers are like this selected to be among those for thermoplastic Suitable processing conditions not yet melt or practically not thermoplastic deform and in the resulting composite as Reinforcing fibers are present.

Examples of such fibers are glass fibers, Carbon fibers, fibers from various metals and  Metal alloys, from various metal nitrides or -carbides, metal oxide fibers or fibers from organic Polymers such as polyacrylonitrile, polyester, aliphatic and aromatic polyamide or polyimide.

Glass, carbon, metal or are preferably used Aramid fibers.

All materials are suitable as thermoplastic material, which can be reversibly processed thermoplastic. Examples of this are metals and metal alloys, glasses and especially organic materials. With the organic Materials are primarily where appropriate Solvent-containing, but preferably known solvent-free organic thermoplastic Molding compounds.

Examples of thermoplastics are polymers such as Vinyl polymers, e.g. B. polyolefins, polyvinyl esters, Polyvinyl ether, polyacrylic and methacrylates, Polyvinyl aromatics, polyvinyl halides, and the various copolymers, block, graft, Liquid crystal, mixed polymers or polymer mixtures. Special representatives are: Polyethylene, Polypropylene, Polybutenes, polypentenes, polyvinylchloride types, Polymethyl methacrylates, poly (meth) acrylonitrile types, optionally modified polystyrenes or Multi-phase plastics such as ABS. Furthermore polyaddition, Polycondensation, polyoxidation or Cyclization polymers, LC polymers, such as polyamides, Polyurethanes, polyureas, polyimides, polyesters, Polyethers, polyhydantoins, polyphenylene oxides, Polyphenylene sulfides, polysulfones, polycarbonates, and their Mixed forms, their mixtures and combinations with others Polymers or polymer precursors, for example polyamide-6; Polyamide-6.6; Polyethylene terephthalate or bisphenol-A- Polycarbonate.  

However, the polymers mentioned can also be used as Reinforcing fiber material serve when used with deeper melting fibers are processed according to the invention act as thermoplastic parts.

The filaments or staple fibers that make up the yarns can have a practically round cross section or else have other shapes, for example a dumbbell-shaped, kidney-shaped, triangular or tri-or. multilobal Have cross-section. Hollow fibers can also be used deploy.

In particular as thermoplastic fibers, bi- or Use multicomponent fibers, for example from Core / sheath or side / side type or matrix / fibril type.

The semi-finished product according to the invention is by local melting of the matrix fibers so solidified that it is easy can be handled without losing its band shape, but at the same time good drapability, rollability and has portability. The invention Semi-finished products can be stored almost indefinitely and indefinitely, since there are practically no hardening components. The consolidation points are at least along one surface of the belt, but can also run along both surfaces. It can be done in individual cases be sufficient that only a surface fixation of the Band has taken place.

But it is also possible that the local Solidification points practically through the cross section of the entire band. Essential to all of these Embodiments is that the melting of the matrix fibers locally and that the individual matrix fibers and / or Reinforcing fibers are between two Can move consolidation points practically freely. The mean free distance between two fastening points preferably about 1 to 5 cm.  

The density of the solidification points along the surface is determined, among other things, by the type and amount of Thermoplastic fibers and the quantitative ratio of thermoplastic and reinforcing fibers depend. It is also possible to get one Applying patterns of solidification points to the tape, d. H. using only parts of the surface of the tape To provide solidification points.

Usual values for the density of consolidation points, based on the unit area of the strip surface, are in the range from 40 to 500,000 points / m ² surface, preferably 100 to 40,000 points / m ² surface (with one-sided application of consolidation points to the surface; with two-sided Applying usually half the density per surface is sufficient). A consolidation point preferably connects several reinforcing yarns.

The volume ratio of the reinforcement to the matrix fibers in the semifinished product according to the invention can be within wide limits can be chosen arbitrarily. So the volume fraction of the Reinforcing fibers e.g. B. 10 to 90% and the Volume share of the matrix fibers accordingly 90 to 10%. The volume fraction is preferably Reinforcing fibers 20-80%, especially 40-70%.

Preferred embodiments of the semi-finished product according to the invention are presented in claims 2 to 7.

The semi-finished product according to the invention can be produced by one

• a) a band-shaped arrangement of essentially unidirectional reinforcement fibers and out thermoplastic matrix fibers in the form of a thread chain provides arranged yarns, and
• b) locally limited to at least one of the surfaces thereof Arrangement generates elevated temperatures, possibly in Combination with increased pressures, so that the matrix fibers melt or melt at these points and local ones Form consolidation points.

The procedure is also the subject of the present Invention. The generation of locally elevated temperatures can by treating the band-shaped arrangement with heated ones Embossing rollers take place. The thread can be between two Embossing rollers or in particular between a roller smooth surface and a roller with structured Surface or partially textured surface be passed through. Generating locally elevated Temperatures can also be in any other way and manner, for example by the action of Hot gas flows or from heated stamps or from Ultrasound or high frequency electromagnetic Radiation (high frequency welding).

These latter two embodiments are special preferred, because with them a practically unlimited Number of patterns at solidification points can be achieved, for example by routing the heating sources to specified ones Because of the surface of the belt and through targeted on and Switch off the heating source. This control can e.g. More colorful Control of a computer.

In Fig. 1a, 1b, 2a and 2b show two embodiments of the inventive method are exemplified.

In Fig. 3 an embodiment of the semi-finished product according to the invention is shown as an example.

Fig. 1a relates to an embodiment in supervision, while this embodiment is shown in Fig. 1b in side view.

The unidirectional yarn sheet ( 2 ) running from a warp beam ( 1 ) (shown in FIG. 1a only over part of the entire warp beam length) consists of at least one type of thermoplastic fiber, such as polyester, polyethylene, polyamide, polyphenylene sulfide, polypropylene, Polyetherimide, polyetherketone, polysulfone or partially halogenated polyolefin fiber, and at least one type of reinforcing fiber such as glass, carbon, metal, ceramic or aramid fiber.

The unidirectional yarn group ( 2 ) is passed between the heated embossing rollers ( 3 ) and ( 4 ). One of these rollers can also have a smooth surface. Under the influence of pressure and heat at the locations of the raised parts of the embossing roller, local melting of the thermoplastic fiber occurs and thus melting points between two or more warp yarns lying next to one another. After leaving the area of the embossing rollers ( 3 ) and ( 4 ), the melting zones solidify and result in a positive connection between these warp yarns.

In Fig. 1a these solidified local melting zones ( 5 ) are shown in the form of a stripe pattern. After solidification, the band ( 6 ) can be wound onto a roll ( 7 ).

Fig. 2a relates to another embodiment in supervision, while this embodiment is shown in Fig. 2b in side view.

The unidirectional yarn sheet ( 2 ) running from a warp beam ( 1 ) (shown in FIG. 2a only over part of the entire warp beam length) consists of at least one type of thermoplastic fiber, e.g. B. such fibers as exemplified in the description of Fig. 1a.

The unidirectional group of yarn ( 2 ) is carried out between a suitable base ( 8 ) and the selective melting unit ( 9 ). Such a selective melting unit can, for. B. an ultrasonic probe, a hot gas supply, a heated stamp or an electromagnetic energy source. The melting unit can be moved parallel to the warp beam axis and in the vertical direction, a computer can control this process as well as switch the energy supply on and off. Likewise, the use of several melting units on a base as well as the use of several combinations consisting of the melting unit (s) and the base (s) in succession is possible. As a result, a higher throughput of the plant can be achieved.

The support (s) can be moved vertically (8a) in order to adjust the diameter changes of the warp beam winding and the roller ( 7 ).

Under the influence of heat at the locations of the reflow unit ( 9 ), the thermoplastic fiber melted locally and thus to fusion points between two or more warp yarns lying side by side. After leaving the area of the melting unit ( 9 ), the melting zones solidify and result in a positive connection between these warp yarns.

In Fig. 2a these solidified local melting zones ( 5 ) are shown in the form of a stripe pattern. After solidification, the band ( 6 ) can be wound onto a roll ( 7 ).

In Fig. 3, an embodiment of the preform according to the invention. The band ( 6 ) is made up of a group of yarn ( 2 ). In this embodiment, mixed yarns ( 10 ) made of reinforcing and matrix fibers are used as yarns. The band ( 6 ) has solidified local melting zones ( 5 ), on each of which two adjacent yarns are connected to each other.

Claims (11)

1. Band of substantially unidirectionally oriented reinforcing fibers and thermoplastic matrix fibers, characterized in that it is essentially composed of yarns containing reinforcing fibers and / or matrix fibers, the yarn density of the tape is about 5 to 20 yarns / cm width, the yarn titer is about Is 1000 to 3000 dtex and the matrix fibers are locally melted or melted on at least one belt surface, forming solidification points. 2. Band according to claim 1, characterized in that it consists of a mixture of yarns made of reinforcing fibers and Yarn is made up of matrix fibers. 3. Band according to claim 1, characterized in that it as Mixed yarn is made up of reinforcing and matrix fibers. 4. Band according to claim 1, characterized in that it consists of Bicomponent fibers with one reinforcement and one Matrix component is constructed. 5. Band according to claim 1, characterized in that the Solidification points in one itself regularly repeating patterns are arranged. 6. Tape according to claim 1, characterized in that the Solidification points statistically over the belt surface are distributed. 7. Band according to claim 1, characterized in that the Solidification points about 5 to 50% of the surface of the Band. 8. A method for producing the tape according to claim 1 comprising the steps:

• a) producing an arrangement of essentially unidirectionally oriented reinforcing fibers and of thermoplastic matrix fibers in the form of yarns arranged as a thread chain, and
• b) Generation of locally limited elevated temperatures and possibly increased pressures on at least one of the belt surfaces, so that the matrix fibers melt or melt at these points and local consolidation points form.

9. The method according to claim 8, characterized in that the formation of local consolidation points by means of heated embossing roller takes place. 10. The method according to claim 9, characterized in that the formation of local consolidation points by means of Ultrasound or high frequency electromagnetic Radiation occurs. 11. Use of the tape according to one of claims 1 to 7 for the production of composite materials, in particular of fiber reinforced thermoplastics.